Question

You take a trip to Oklahoma City. The turnpike between Tulsa and OKC

is 90 miles long. You drive slowly for an hour and forty-five minutes, stop
at the rest area for fifteen minutes, then drive very fast from the rest
area to the City, arriving an hour after you left the rest area.
What was your average speed for the trip?

Answer 1

`speed_(avg) = (Σ\:distance)/( total\: time)`

So, according to the question:

distance = 90 miles

time = 1h 45min + 15 min + 1h = 3h

`Therefore:\\ speed_(avg) = (90)/(3) mph \\ = \boxed {30 \: mph}`